1. Field of Invention:
This invention relates to piston rings and more particularly to piston rings for use in internal combustion engines which have their bearing face plasma sprayed with nickel aluminide and a ceramic wear and scuff resistant coating comprised of aluminum oxide and titanium dioxide.
2. Description of the Prior Art
Since internal combustion engines such as diesel engines having higher power and speeds are coming into service, piston ring bearing faces have been coated with various materials to improve their wear characteristics. Chromium has been used as a coating material for many years. However, chromium is relatively expensive especially when compared to the scuff and wear resistance it provides.
U.S. Pat. No. 3,697,091 discloses a coating comprised essentially of a mixture of aluminum oxide and titanium dioxide in specified percentages by weight. Although the coating disclosed in U.S. Pat. No. 3,697,091 did exhibit a certain degree of good wear and scuff resistance in tests, it is believed that these compositions do not exhibit the superior qualities demonstrated by the compositions of the present application. Further, it does not appear that the compositions of U.S. Pat. No. 3,697,091 have found commercial acceptance.
Copending application Ser. No. 759,841 filed Jan. 17, 1977, discloses and claims a ceramic coating comprised of aluminum oxide and relatively small percentages by weight of titanium dioxide and ferric oxide. This ceramic coating demonstrates both a high degree of wear and scuff resistance.